EP3538678A1 - Method for producing a rolling bearing ring having an improved robustness against the formation of white etching cracks (wec) - Google Patents

Method for producing a rolling bearing ring having an improved robustness against the formation of white etching cracks (wec)

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Publication number
EP3538678A1
EP3538678A1 EP17811833.7A EP17811833A EP3538678A1 EP 3538678 A1 EP3538678 A1 EP 3538678A1 EP 17811833 A EP17811833 A EP 17811833A EP 3538678 A1 EP3538678 A1 EP 3538678A1
Authority
EP
European Patent Office
Prior art keywords
rolling bearing
tempering
bearing ring
formation
hardened
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP17811833.7A
Other languages
German (de)
French (fr)
Other versions
EP3538678B1 (en
Inventor
Lothar Hofmann
Andreas Mangold
Toni BLAß
Wolfram Kruhöffer
Werner Trojahn
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Schaeffler Technologies AG and Co KG
Original Assignee
Schaeffler Technologies AG and Co KG
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Publication of EP3538678A1 publication Critical patent/EP3538678A1/en
Application granted granted Critical
Publication of EP3538678B1 publication Critical patent/EP3538678B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06—Surface hardening
    • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
    • C21D1/10—Surface hardening by direct application of electrical or wave energy; by particle radiation by electric induction
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/36—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for balls; for rollers
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/38—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for roll bodies
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30—Parts of ball or roller bearings
    • F16C33/58—Raceways; Race rings
    • F16C33/62—Selection of substances
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
    • F16C33/30—Parts of ball or roller bearings
    • F16C33/58—Raceways; Race rings
    • F16C33/64—Special methods of manufacture
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2204/00—Metallic materials; Alloys
    • F16C2204/60—Ferrous alloys, e.g. steel alloys
    • F16C2204/64—Medium carbon steel, i.e. carbon content from 0.4 to 0,8 wt%
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the invention relates to a method for producing a rolling bearing ring with improved robustness against the formation of white etching cracks (WEC).
  • WEC white etching cracks
  • Rolling bearings are used in a wide variety of applications, for example in the automotive sector or in industrial plants or machines and the like.
  • the stress of such a rolling bearing includes not only the classic stress, so the rolling of the bearing rings by the rolling elements and the associated Herz'schen pressure or the Herz'schen contact, often also an additional stress, for example, a strong mixed friction or an electrical see or dynamic electricity or the like can be.
  • additional stress for example, a strong mixed friction or an electrical see or dynamic electricity or the like
  • WEC White Etching Cracks
  • These white etching cracks first appear as structural changes in the material of the affected rolling bearing component. The structural change takes place below the bearing surface, ie the loaded surface.
  • microcracks can form under the influence of the external load and spread to the surface.
  • the microcracks then give the typical WEC damage pattern in the form of axial cracks or exfoliations, preferably in the region of the track of the loaded component, for example an inner or outer ring of a rolling bearing. In extreme cases, as the damage progresses, it can lead to breakage or breakage of the rolling bearing ring and thus premature bearing failure.
  • a method for producing a rolling bearing component in which the rolling bearing component is heated to a temperature between 100-200 ° C. for a time of 5-120 min., During which time it is in contact in the region of the raceway with a chemical additive comes to form a locally superficially modified raceway layer.
  • a chemical additive a preservative or gear oil having a water content of up to 500 ppm may be used.
  • Such a surface modification is effective against the formation of WECs only as long as it is not worn away during operation.
  • the use of such components is limited, especially in applications in polluted environment and / or with a high Mitakingsanteil only possible.
  • WO 2015/199 599 A1 describes a method for surface hardening a metal component with the steps of induction hardening and subsequent tempering. The situation is similar with the application of special coatings or the formation of a burnishing layer on the running surfaces, ie the claimed component areas. These may eventually lose their function when rubbed off.
  • the invention is therefore based on the problem to provide a method that allows the production of a rolling bearing ring with improved robustness against the formation of white etching cracks.
  • a method is provided according to the invention, which is characterized in that the rolling bearing ring of a hypoeutectoid tempering steel containing C to 0.4 - 0.55% and Cr to 0.5 - 2.0% to form a hardened surface layer inductive heated, then quenched and then tempered.
  • the method according to the invention envisages the use of a special starting material, namely a hypoeutectoid tempering steel, and, on the other hand, the implementation of defined hardening and temperature treatment steps, which lead to the formation of a hardened surface layer.
  • the steel used according to the invention is a hypoeutectoid tempering steel having a carbon content of 0.4-0.55% and a chromium content of 0.5-2.0%. Such a hypoeutectic tempering steel is then hardened in an inductive hardening process exclusively on the edge, so that an inductively hardened surface layer is formed. When hardened, this hypoeutectoid tempering steel does not contain undissolved carbides in the hardened surface area. After induction heating, quenching of the rolling bearing component takes place (hardening), followed by a tempering step. Tempering produces the smallest tempering carbides (Fe2C) whose size is well below 1 pm.
  • Fe2C tempering carbides
  • the heating can be done evenly over the surface to be hardened or in the feed process.
  • the electrical power required for heating is controlled so that it does not come to re-heating when reaching an already hardened area, the deterrent is also in the feed by means of a shower.
  • the structure below the hardened surface layer of the rolling bearing ring according to the invention in contrast to classic, through hardened bearing steels such as from the 100Cr6 family not from Plattenmartensit, but from Lanzzartsit.
  • This structure ensures compliance or achievement of the desired mechanical properties of the rolling bearing component, combined with a hardened and robust surface layer.
  • the production is significantly simplified, since only an inductive surface hardening takes place, which can take place much faster than complete curing.
  • the application of special coatings or the production of a surface-modified tread and the like, as provided in the prior art is not required, which is why the rolling bearing component is very simple and fast producible.
  • the tempering steel used may have a content of Ni of 0.5 to 1, 0%.
  • the hypo-tectoid tempering steel thus shows a defined, relatively high Ni content.
  • This Ni content leads to an increase in the toughness and thus to a further improvement of the achievable mechanical properties.
  • the C content can be reduced somewhat, which is additionally advantageous in that, as stated, there are no undissolved carbides in the cured state.
  • a tempering steel with the following composition is preferably used according to the invention (data in%):
  • the inductive heating can take place in such a way that a hardened edge layer of at least 0.2 mm thickness to at most 8 mm thickness is formed.
  • the thickness of the boundary layer depends on the dimension of the rolling bearing ring.
  • the inductive heating takes place at a frequency of 8-1 1 kHz, in particular 9-10 kHz for a duration of 3-10 s, in particular 4-7 s. Curing at 9.9 kHz for 5 seconds is particularly preferred.
  • Inductive hardening leads to high compressive stresses developing in the hardened edge area.
  • the hardening should take place according to the invention such that a compressive residual stress of at least 300 MPa, or significantly higher, is given in the hardened edge region. With increasing compressive residual stress, the barrier effect of the surface layer increases against hydrogen diffusion.
  • the tempering which leads to the formation of the tempering carbides, should take place at a temperature of 120-160 ° C., in particular at 130-150 ° C. for a period of 1-4 hours, in particular 2-3 hours. Particularly preferably, the tempering takes place at a temperature of 140 ° C for 2 h.
  • the quenching preceding the tempering takes place in a suitable quenching liquid.
  • the invention further relates to a rolling bearing ring, which is produced according to the inventive method. It consists of a non-eutectoid tempering steel containing C at 0.4 - 0.55% and Cr at 0.5 - 2.0% with a hardened surface layer formed by inductive hardening.
  • the rolling bearing ring may be in development of the invention of a tempering steel based on 50CrMo4 with a Ni content between 0.5 - 1, 0%, it may preferably have the following composition (in%):
  • a first batch of six thrust bearings was made from a commercially available 100Cr6 steel with the following manufacturing route:
  • the bearings each consisted of two thrust washers with an outer diameter of 95 mm and an inner diameter of 60 mm.
  • the rolling elements were ceramic cylindrical rollers with a length of 1 1 mm and a diameter of 1 1 mm. They were in a cage.
  • the life test was carried out according to DIN51819-1, but with a revolution of 750 rpm, a load of 60 kN (2075 MPa) and the presence of a special, WEC-producing oil.
  • two rolling bearings of the same type were investigated, ie in each case two bearings according to the invention the modified 50CrMo4 or two bearings from previously used 100Cr6.
  • Ni-containing hypoeutrogenic tempering steel according to the invention in conjunction with the production route according to the invention or, in particular, the inductive surface hardening, a considerable improvement in the transit time could be achieved, compared with the martensitic thrust bearing disks made of 100Cr6.
  • the result is a runtime increase of more than a factor of 2, as results from a comparison of the average maturities.
  • the bearings made of 100Cr6 give an average transit time of 43h, calculated over all 6 bearings, while the bearings according to the invention have an average runtime of 98 hours, rather than more than twice that.
  • the employed comparative investigations show that the method according to the invention respectively the rolling bearing component according to the invention shows a clear improvement of the robustness against the formation of WECs. This is also shown by the Weibull representation of the measured values shown in the drawing. Plotted along the abscissa is the life, ie the operating time to failure and along the ordinate the so-called unreliability value, which indicates the probability of failure Hi in percent, each logarithmic.
  • the Weibull distribution represents a general distribution.
  • Hi (i - 0.3): (n + 0.4) with:
  • n number of samples (here: 6)
  • the measured values ( ⁇ ) shown as squares indicate the values for the rolling bearings or axial discs made of 100Cr6.
  • the diamond-shaped symbols ( ⁇ ) represent the measured values for the rolling bearing components according to the invention or axial disks. Also shown is a fitness straight.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Articles (AREA)
  • Rolling Contact Bearings (AREA)

Abstract

The invention relates to a method for producing a rolling bearing ring having an improved robustness against the formation of white etching cracks (WEC), wherein the rolling bearing component, which is made of a sub-eutectoid, heat-treated steel containing 0.4 - 0.55 % of C and 0.5 - 2.0 % of Cr is inductively heated for forming a hardened boundary layer, then quenched and subsequently tempered.

Description

Verfahren zur Herstellung eines Wälzlagerrings mit verbesserter Robustheit gegen die Bildung von White Etching Cracks (WEC)  Method for producing a rolling bearing ring with improved robustness against the formation of white etching cracks (WEC)
Die Erfindung betrifft ein Verfahren zur Herstellung eines Wälzlagerrings mit verbesserter Robustheit gegen die Bildung von White Etching Cracks (WEC). The invention relates to a method for producing a rolling bearing ring with improved robustness against the formation of white etching cracks (WEC).
Wälzlager kommen in unterschiedlichsten Anwendungen zum Einsatz, beispielsweise im Automobilbereich oder bei Industrieanlagen oder -maschinen und Ähnlichem. Die Beanspruchung eines solchen Wälzlagers umfasst neben der klassischen Beanspruchung, also der Überrollung der Lagerringe durch die Wälzkörper und der damit verbundenen Herz'schen Pressung respektive dem Herz'schen Kontakt, oft auch eine Zusatzbeanspruchung, die beispielsweise eine starke Mischreibung oder eine elektri- sehe oder dynamische Elektrizität oder Ähnliches sein kann. Insbesondere wenn eine solche Zusatzbeanspruchung vorliegt, haben sich im Anwendungsfall mitunter Schäden an solchen Wälzlagern respektive den Wälzlagerbauteilen in Form sogenannter White Etching Cracks (WEC) gezeigt. Diese White Etching Cracks treten zunächst als Gefügeveränderungen im Werkstoff der betroffenen Wälzlagerkomponente auf. Die Gefügeveränderung findet unterhalb der Lageroberfläche, also der belasteten Fläche statt. Im weiteren Verlauf können sich Mikrorisse unter dem Einfluss der äußeren Belastung bilden und bis zur Oberfläche hin ausbreiten. Die Mikrorisse ergeben dann das für WECs typische Schadensbild in Form von Axialrissen oder Abblätterungen, bevorzugt im Bereich der Laufbahn des belasteten Bauteils, beispielsweise eines In- nen- oder Außenrings eines Wälzlagers. Im Extremfall kann es bei fortschreitendem Schadensverlauf bis zu einem Reißen oder Brechen des Wälzlagerrings und damit einem vorzeitigen Lagerausfall kommen. Rolling bearings are used in a wide variety of applications, for example in the automotive sector or in industrial plants or machines and the like. The stress of such a rolling bearing includes not only the classic stress, so the rolling of the bearing rings by the rolling elements and the associated Herz'schen pressure or the Herz'schen contact, often also an additional stress, for example, a strong mixed friction or an electrical see or dynamic electricity or the like can be. In particular, when such additional stress is present, in the application, sometimes damage to such bearings respectively the rolling bearing components in the form of so-called White Etching Cracks (WEC) have been shown. These white etching cracks first appear as structural changes in the material of the affected rolling bearing component. The structural change takes place below the bearing surface, ie the loaded surface. In the further course, microcracks can form under the influence of the external load and spread to the surface. The microcracks then give the typical WEC damage pattern in the form of axial cracks or exfoliations, preferably in the region of the track of the loaded component, for example an inner or outer ring of a rolling bearing. In extreme cases, as the damage progresses, it can lead to breakage or breakage of the rolling bearing ring and thus premature bearing failure.
Der Schadensmechanismus, der zur Bildung solcher WECs führt, ist noch nicht ab- schließend geklärt. Es wird jedoch davon ausgegangen, dass die Zusatzbeanspruchung zu einer Freisetzung von Wasserstoff aus dem Schmierstoffsystem, über welches das Wälzlager geschmiert wird, führt. Dieser Wasserstoff führt vermutlich im Gefüge des Wälzlagermaterials, also des Stahls, zur Umwandlung von martensitischen und/oder bainitischen Strukturen zu amorphem bzw. nanokristallinem Ferrit mit zwangsgelöstem Kohlenstoff bzw. aufgelösten Carbidstrukturen. The damage mechanism leading to the formation of such WECs has not yet been fully clarified. However, it is believed that the extra stress results in a release of hydrogen from the lubricant system over which the bearing is lubricated. This hydrogen probably leads to the transformation of martensitic material in the structure of the rolling bearing material, ie the steel and / or bainitic structures to amorphous or nanocrystalline ferrite with positively dissolved carbon or dissolved carbide structures.
Aus EP 2 123 779 A1 ist bekannt, ein mechanisch belastetes Lagerbauteil aus einem durchgehärteten Stahl mit einem Kohlenstoffgehalt zwischen 0,4 - 0,8 Gew.% herzustellen. Das Durchhärten ist aber abhängig von z.B. dem Gehalt an härtbarkeitsstei- gernden Legierungselementen auf einen bestimmten Querschnitt beschränkt. Außerdem ist dieses Technologie nicht einsetzbar, wenn das Bauteil nach dem Härten eine hohe Zähigkeit im Kern aufweisen soll. It is known from EP 2 123 779 A1 to produce a mechanically loaded bearing component made of a hardened steel with a carbon content of between 0.4 and 0.8% by weight. The hardening is, however, dependent on e.g. the content of hardenability-increasing alloying elements limited to a certain cross-section. In addition, this technology is not applicable if the component should have a high toughness in the core after curing.
Aus EP 2 573 195 A1 ist ein Verfahren zur Herstellung eines Wälzlagerbauteils bekannt, bei dem das Wälzlagerbauteil auf eine Temperatur zwischen 100 - 200 °C für eine Zeit von 5 - 120 Min. erwärmt wird, während welcher Zeit es im Bereich der Laufbahn in Kontakt mit einem chemischen Additiv kommt, um eine lokal oberflächlich veränderte Laufbahnrandschicht auszubilden. Als ein solches chemisches Additiv kann ein Konservierungs- oder ein Getriebeöl mit einem Wassergehalt von bis zu 500 ppm verwendet werden. Eine solche Oberflächenmodifikation ist jedoch nur solange gegen die Bildung von WECs wirksam, solange sie nicht im Betrieb abgerieben ist. Damit ist der Einsatz solcher Bauteile insbesondere bei Anwendungen in verschmutz- ter Umgebung und/oder mit hohem Mischreibungsanteil nur eingeschränkt möglich. From EP 2 573 195 A1 a method for producing a rolling bearing component is known, in which the rolling bearing component is heated to a temperature between 100-200 ° C. for a time of 5-120 min., During which time it is in contact in the region of the raceway with a chemical additive comes to form a locally superficially modified raceway layer. As such a chemical additive, a preservative or gear oil having a water content of up to 500 ppm may be used. Such a surface modification, however, is effective against the formation of WECs only as long as it is not worn away during operation. Thus, the use of such components is limited, especially in applications in polluted environment and / or with a high Mischreibungsanteil only possible.
Die WO 2015/ 199 599 A1 beschreibt ein Verfahren zur Oberflächenhärtung einer Metallkomponente mit den Schritten Induktionshärten und anschließendem Anlassen. Ähnlich verhält es sich bei Aufbringen von speziellen Beschichtungen oder dem Ausbilden einer Brünierschicht auf den Laufflächen, also den beanspruchten Bauteilbereichen. Diese können gegebenenfalls ihre Funktion verlieren, wenn sie abgerieben sind. WO 2015/199 599 A1 describes a method for surface hardening a metal component with the steps of induction hardening and subsequent tempering. The situation is similar with the application of special coatings or the formation of a burnishing layer on the running surfaces, ie the claimed component areas. These may eventually lose their function when rubbed off.
Der Erfindung liegt damit das Problem zugrunde, ein Verfahren anzugeben, das die Herstellung eines Wälzlagerrings mit einer verbesserten Robustheit gegen die Bildung von White Etching Cracks ermöglicht. Zur Lösung dieses Problems ist erfindungsgemäß ein Verfahren vorgesehen, das sich dadurch auszeichnet, dass der Wälzlagerring aus einem untereutektoiden Vergütungsstahl enthaltend C zu 0,4 - 0,55 % und Cr zu 0,5 - 2,0 % zur Ausbildung einer gehärteten Randschicht induktiv erwärmt, anschließend abgeschreckt und anschlie- ßend angelassen wird. The invention is therefore based on the problem to provide a method that allows the production of a rolling bearing ring with improved robustness against the formation of white etching cracks. To solve this problem, a method is provided according to the invention, which is characterized in that the rolling bearing ring of a hypoeutectoid tempering steel containing C to 0.4 - 0.55% and Cr to 0.5 - 2.0% to form a hardened surface layer inductive heated, then quenched and then tempered.
Das erfindungsgemäße Verfahren sieht einerseits die Verwendung eines besonderen Ausgangsmaterials, nämlich eines untereutektoiden Vergütungsstahls vor, zum anderen die Durchführung definierter Härte- und Temperaturbehandlungsschritte, die zur Ausbildung einer gehärteten Randschicht führen. On the one hand, the method according to the invention envisages the use of a special starting material, namely a hypoeutectoid tempering steel, and, on the other hand, the implementation of defined hardening and temperature treatment steps, which lead to the formation of a hardened surface layer.
Als Stahl wird erfindungsgemäß ein untereutektoider Vergütungsstahl mit einem Kohlenstoffgehalt von 0,4 - 0,55 % und einem Chromgehalt von 0,5 - 2,0 % verwendet. Ein solcher untereutektoider Vergütungsstahl wird sodann in einem induktiven Härteverfahren ausschließlich randseitig gehärtet, so dass sich eine induktiv gehärtete Randschicht ausbildet. Im gehärteten Zustand enthält dieser untereutektoide Vergütungsstahl im gehärteten Randschichtbereich keine ungelösten Carbide. Nach dem Induktiverwärmen erfolgt ein Abschrecken des Wälzlagerbauteils (Härten), woran sich ein Anlassschritt anschließt. Durch das Anlassen werden kleinste Anlasscarbide (Fe2C) gebildet, deren Größe deutlich unter 1 pm ist. The steel used according to the invention is a hypoeutectoid tempering steel having a carbon content of 0.4-0.55% and a chromium content of 0.5-2.0%. Such a hypoeutectic tempering steel is then hardened in an inductive hardening process exclusively on the edge, so that an inductively hardened surface layer is formed. When hardened, this hypoeutectoid tempering steel does not contain undissolved carbides in the hardened surface area. After induction heating, quenching of the rolling bearing component takes place (hardening), followed by a tempering step. Tempering produces the smallest tempering carbides (Fe2C) whose size is well below 1 pm.
Durch die induktive Randschichthärtung sind in der Randschicht sehr hohe Druckeigenspannungen gegeben, die eine gewisse Sperrwirkung für Wasserstoff darstellen, der als Ursache für die Bildung der WECs angesehen wird. Das heißt, dass trotz der gegebenen Zusatzbeanspruchung und der hieraus möglicherweise resultierenden Bildung von Wasserstoff dieser nicht in das Gefüge diffundieren kann, weshalb sich der derart hergestellte Wälzlagerring als äußerst robust gegen die Bildung von WECs erwiesen hat. Ein weiterer Vorteil der durch die Induktivhärtung gegebenen hohen Druckeigenspannungen ist, dass sie bei einer Überrollung entstehende Zugdehnungs- felder überkompensieren, so dass auch hierüber die Anlagerung von Wasserstoff in diesen Bereichen gehemmt ist. Durch die hohen Druckeigenspannungen wird letztlich die absolute Wasserstoffkonzentration und damit der schädliche Einfluss im überrollten Volumen signifikant verringert. Das Erwärmen kann gleichmäßig über der zu härtenden Fläche erfolgen oder im Vorschubverfahren. Für das Vorschubverfahren wird die zur Erwärmung erforderliche elektrische Leistung so gesteuert, dass es beim Erreichen eines bereits gehärteten Bereichs nicht zu dessen Wiedererwärmung kommt, die Abschreckung erfolgt ebenfalls im Vorschub mittels einer Brause. Due to the inductive surface hardening, very high compressive residual stresses are present in the surface layer, which represent a certain blocking effect for hydrogen, which is considered to be the cause of the formation of the WECs. This means that in spite of the given additional stress and the resulting possible formation of hydrogen this can not diffuse into the structure, which is why the rolling bearing ring thus produced has proven to be extremely robust against the formation of WECs. A further advantage of the high residual compressive stresses given by inductive hardening is that they overcompensate tensile strain fields that arise during rolling over, so that the addition of hydrogen in these regions is also inhibited. Due to the high residual compressive stresses, the absolute hydrogen concentration and thus the harmful influence in the overrun volume are significantly reduced. The heating can be done evenly over the surface to be hardened or in the feed process. For the feed process, the electrical power required for heating is controlled so that it does not come to re-heating when reaching an already hardened area, the deterrent is also in the feed by means of a shower.
Das Gefüge unterhalb der gehärteten Randschicht des erfindungsgemäßen Wälzlagerrings besteht im Gegensatz zu klassischen, durchgehärteten Wälzlagerstählen wie beispielsweise aus der 100Cr6-Familie nicht aus Plattenmartensit, sondern aus Lan- zettmartensit. Dieses Gefüge stellt die Einhaltung respektive das Erreichen der gewünschten mechanischen Eigenschaften des Wälzlagerbauteils sicher, verbunden mit einer gehärteten und robusten Randschicht. Die Herstellung ist deutlich vereinfacht, da lediglich eine induktive Randschichthärtung erfolgt, die wesentlich schneller vonstattengehen kann als eine vollständige Durchhärtung. Auch ist das Aufbringen spezieller Beschichtungen oder die Erzeugung einer oberflächenmodifizierten Lauffläche und Ähnliches, wie im Stand der Technik vorgesehen, nicht erforderlich, weshalb das Wälzlagerbauteil sehr einfach und schnell her- stellbar ist. The structure below the hardened surface layer of the rolling bearing ring according to the invention, in contrast to classic, through hardened bearing steels such as from the 100Cr6 family not from Plattenmartensit, but from Lanzzartensit. This structure ensures compliance or achievement of the desired mechanical properties of the rolling bearing component, combined with a hardened and robust surface layer. The production is significantly simplified, since only an inductive surface hardening takes place, which can take place much faster than complete curing. Also, the application of special coatings or the production of a surface-modified tread and the like, as provided in the prior art, is not required, which is why the rolling bearing component is very simple and fast producible.
Gemäß einer besonders zweckmäßigen Weiterbildung der Erfindung kann der verwendete Vergütungsstahl einen Gehalt an Ni von 0,5 - 1 ,0 % aufweisen. Der untereu- tektoide Vergütungsstahl zeigt also einen definierten, relativ hohen Ni-Gehalt. Dieser Ni-Gehalt führt zu einer Steigerung der Zähigkeit und damit zu einer weiteren Verbesserung der erreichbaren mechanischen Eigenschaften. Durch Erhöhung des Ni- Gehalts kann gleichzeitig der C-Gehalt etwas verringert werden, was zusätzlich dahingehend von Vorteil ist, dass, wie ausgeführt, im gehärteten Zustand keine ungelösten Carbide vorliegen. According to a particularly advantageous embodiment of the invention, the tempering steel used may have a content of Ni of 0.5 to 1, 0%. The hypo-tectoid tempering steel thus shows a defined, relatively high Ni content. This Ni content leads to an increase in the toughness and thus to a further improvement of the achievable mechanical properties. At the same time, by increasing the Ni content, the C content can be reduced somewhat, which is additionally advantageous in that, as stated, there are no undissolved carbides in the cured state.
Besonders bevorzugt wird ein Vergütungsstahl auf Basis von 50CrMo4 mit einem Ni- Gehalt zwischen 0,5 - 1 ,0 % verwendet. Im Vergleich zu dem bekannten Vergütungsstahl 50CrMo4, dessen C-Gehalt zwischen 0,46 - 0,54 % liegt, liegt aufgrund des Ni- Gehalts der C-Gehalt etwas niedriger. Das heißt, dass bevorzugt ein Vergütungsstahl folgender Zusammensetzung verwendet wird (Angaben in %): Particular preference is given to using a tempering steel based on 50CrMo4 with a Ni content of between 0.5-1.0%. Compared to the well-known 50CrMo4 tempering steel, whose C content is between 0.46 and 0.54%, the Salary of C content slightly lower. This means that preference is given to using a tempering steel of the following composition (data in%):
C: < 0,46  C: <0.46
Si: max. 0,4  Si: max. 0.4
Mn: 0,5 - 0,8  Mn: 0.5 - 0.8
P: max. 0,035  P: max. 0,035
S: max. 0,03  S: max. 0.03
Cr: 0,9 - 1 ,2  Cr: 0.9-1.2
Mo: 0, 15 - 0,3  Mo: 0, 15 - 0.3
Ni: 0,5 - 1 ,0.  Ni: 0.5-1.0.
In einem konkreten Ausführungsbeispiel wird erfindungsgemäß bevorzugt ein Vergütungsstahl mit folgender Zusammensetzung verwendet (Angaben in %): In a concrete exemplary embodiment, a tempering steel with the following composition is preferably used according to the invention (data in%):
C: 0,45  C: 0.45
Si: 0,23  Si: 0.23
Mn: 0,64  Mn: 0.64
P: 0,004  P: 0.004
S: 0,001  S: 0.001
Cr: 1 , 18  Cr: 1, 18
Mo: 0,28  Mo: 0.28
Ni: 0,75  Ni: 0.75
Cu: 0, 12  Cu: 0, 12
AI: 0,02  AI: 0.02
sowie ein Rest aus Eisen und Spurenelementen.  and a balance of iron and trace elements.
Gemäß einer zweckmäßigen Weiterbildung des erfindungsgemäßen Verfahrens kann vorgesehen sein, dass das induktive Erwärmen derart erfolgt, dass sich eine gehärtete Randschicht von wenigstens 0,2 mm Dicke bis höchstens 8 mm Dicke ausbildet. Die Dicke der Randschicht hängt natürlich von der Bemaßung des Wälzlagerrings ab. Die induktive Randschichthärtung erfolgt dabei insbesondere bei größeren Querschnitten respektive größeren Bauteilen und damit größeren Randschichthärtetiefen vorzugsweise an vorvergüteten Stählen, aber auch eine Härtung aus dem Nor- malglühgefüge oder dem GKZ-Zustand ist möglich (GKZ = Glühen auf kugeligen Ze- mentit). According to an expedient development of the method according to the invention, provision can be made for the inductive heating to take place in such a way that a hardened edge layer of at least 0.2 mm thickness to at most 8 mm thickness is formed. Of course, the thickness of the boundary layer depends on the dimension of the rolling bearing ring. The inductive surface hardening is carried out in particular for larger cross-sections or larger components and thus larger surface hardening depths preferably on pre-tempered steels, but also a hardening from the Nor- sometimes annealed or GKZ state is possible (GKZ = annealing on spherical cementite).
Das induktive Erwärmen erfolgt bei einer Frequenz von 8 - 1 1 kHz, insbesondere von 9 - 10 kHz für eine Dauer von 3 - 10 s, insbesondere 4 - 7 s. Besonders bevorzugt wird eine Härtung bei 9,9 kHz für 5 s. The inductive heating takes place at a frequency of 8-1 1 kHz, in particular 9-10 kHz for a duration of 3-10 s, in particular 4-7 s. Curing at 9.9 kHz for 5 seconds is particularly preferred.
Die induktive Härtung führt dazu, dass sich im gehärteten Randbereich hohe Druckeigenspannungen ausbilden. Das Härten sollte erfindungsgemäß derart erfolgen, dass im gehärteten Randbereich eine Druckeigenspannung von wenigstens 300 MPa, oder deutlich höher gegeben ist. Mit zunehmender Druckeigenspannung steigt die Sperrwirkung der Randschicht gegen eine Wasserstoffdiffusion. Inductive hardening leads to high compressive stresses developing in the hardened edge area. The hardening should take place according to the invention such that a compressive residual stress of at least 300 MPa, or significantly higher, is given in the hardened edge region. With increasing compressive residual stress, the barrier effect of the surface layer increases against hydrogen diffusion.
Das Anlassen, das zur Bildung der Anlasscarbide führt, sollte bei einer Temperatur von 120 - 160 °C, insbesondere bei 130 - 150 °C für eine Dauer von 1 - 4 h, insbesondere 2 - 3 h erfolgen. Besonders bevorzugt erfolgt das Anlassen bei einer Temperatur von 140 °C für 2 h. Das dem Anlassen vorgeschaltete Abschrecken erfolgt in einer geeigneten Abschreckflüssigkeit. Neben dem Verfahren selbst betrifft die Erfindung ferner einen Wälzlagerring, das gemäß dem erfindungsgemäßen Verfahren hergestellt ist. Es besteht aus einem un- tereutektoiden Vergütungsstahl enthaltend C zu 0,4 - 0,55 % und Cr zu 0,5 - 2,0 % mit einer durch induktives Härten ausgebildeten gehärteten Randschicht. Der Wälzlagerring kann in Weiterbildung der Erfindung aus einem Vergütungsstahl auf Basis von 50CrMo4 mit einem Ni-Gehalt zwischen 0,5 - 1 ,0 % sein, es kann vorzugsweise folgende Zusammensetzung besitzen (Angaben in %): The tempering, which leads to the formation of the tempering carbides, should take place at a temperature of 120-160 ° C., in particular at 130-150 ° C. for a period of 1-4 hours, in particular 2-3 hours. Particularly preferably, the tempering takes place at a temperature of 140 ° C for 2 h. The quenching preceding the tempering takes place in a suitable quenching liquid. In addition to the process itself, the invention further relates to a rolling bearing ring, which is produced according to the inventive method. It consists of a non-eutectoid tempering steel containing C at 0.4 - 0.55% and Cr at 0.5 - 2.0% with a hardened surface layer formed by inductive hardening. The rolling bearing ring may be in development of the invention of a tempering steel based on 50CrMo4 with a Ni content between 0.5 - 1, 0%, it may preferably have the following composition (in%):
C: 0,45  C: 0.45
Si: 0,23  Si: 0.23
Mn: 0,64  Mn: 0.64
P: 0,004  P: 0.004
S: 0,001  S: 0.001
Cr: 1 , 18 Mo: 0,28 Cr: 1, 18 Mo: 0.28
Ni: 0,75  Ni: 0.75
Cu: 0, 12  Cu: 0, 12
AI: 0,02  AI: 0.02
sowie ein Rest aus Eisen und Spurenelementen.  and a balance of iron and trace elements.
Es wurden jeweils sechs Axiallager bestehend aus jeweils zwei Axialscheiben herge- In each case, six thrust bearings consisting of two axial disks each were produced.
Ein erstes Konvolut aus sechs Axiallagern wurde aus einem handelsüblichen 100Cr6- Stahl mit folgender Herstellroute hergestellt: A first batch of six thrust bearings was made from a commercially available 100Cr6 steel with the following manufacturing route:
Schmieden - Vergüten - Drehen - martensitisches Härten - Abschrecken - Anlassen - Schleifen - Honen. Ein zweites Konvolut aus sechs Lagern wurde in der erfindungsgemäßen Weise aus einem untereutektoiden Vergütungsstahl folgende Zusammensetzung hergestellt:  Forging - tempering - turning - martensitic hardening - quenching - tempering - grinding - honing. A second batch of six bearings was prepared in the manner according to the invention from a hypoeutectoid tempering steel having the following composition:
C: 0,45  C: 0.45
Si: 0,23  Si: 0.23
Mn: 0,64  Mn: 0.64
P: 0,004  P: 0.004
S: 0,001  S: 0.001
Cr: 1 , 18  Cr: 1, 18
Mo: 0,28  Mo: 0.28
Ni: 0,75  Ni: 0.75
Cu: 0, 12  Cu: 0, 12
AI: 0,02  AI: 0.02
sowie ein Rest aus Eisen und Spurenelementen (Angaben in %).  and a balance of iron and trace elements (in%).
Die Herstellungsroute dieses auf Basis von 50CrMo4 modifizierten untereutektoiden Vergütungsstahls war wie folgt: The production route of this 50CrMo4-modified hypoeutectoid tempered steel was as follows:
Schmieden - GKZ-Glühen - Drehen - induktives Randschichthärten - Anlassen - Schleifen - Honen. Das induktive Härten erfolgte über eine Frequenz von 9,9 kHz bei einer Heizzeit von 5 s. Das Abschrecken erfolgte in einem unter dem Handelsnamen„Aquatensid-BW" erhältlichen Abschreckbad auf Raumtemperatur. Das Anlassen erfolgte bei 140 °C für 2 h. Forging - GKZ annealing - turning - inductive surface hardening - tempering - grinding - honing. The inductive hardening took place over a frequency of 9.9 kHz with a heating time of 5 s. Quenching was carried out in a quench bath available under the trade name "Aquatenside BW" at room temperature and tempered at 140 ° C for 2 hours.
Die Lager bestanden aus jeweils zwei Axiallagerscheiben mit einem Außendurchmesser von 95 mm und einem Innendurchmesser von 60 mm. Die Wälzkörper waren keramische Zylinderrollen mit einer Länge von 1 1 mm und einem Durchmesser von 1 1 mm. Sie waren in einem Käfig geführt. The bearings each consisted of two thrust washers with an outer diameter of 95 mm and an inner diameter of 60 mm. The rolling elements were ceramic cylindrical rollers with a length of 1 1 mm and a diameter of 1 1 mm. They were in a cage.
Die Lebensdaueruntersuchung wurde gemäß den Vorgaben nach DIN51819-1 , jedoch bei einer Umdrehung von 750 U/min, einer Belastung von 60 kN (2075 MPa) und Anwesenheit eines speziellen, WEC-erzeugenden Öls durchgeführt. Es wurden jeweils zwei Wälzlager des gleichen Typs untersucht, also jeweils zwei erfindungsgemäße Lager dem modifizierten 50CrMo4 oder jeweils zwei Lager aus bisher verwendetem 100Cr6. The life test was carried out according to DIN51819-1, but with a revolution of 750 rpm, a load of 60 kN (2075 MPa) and the presence of a special, WEC-producing oil. In each case, two rolling bearings of the same type were investigated, ie in each case two bearings according to the invention the modified 50CrMo4 or two bearings from previously used 100Cr6.
Die erhaltenen Ergebnisse sind in der nachfolgenden Tabelle dargestellt. The results obtained are shown in the following table.
Lager Nr. 100Cr6 50CrMo4 Bearing no. 100Cr6 50CrMo4
Laufzeit in h Laufzeit in h Runtime in h Runtime in h
1 39 74 1 39 74
2 39 74 2 39 74
3 45 106 3 45 106
4 45 106 4 45 106
5 45 1 14 5 45 1 14
6 45 1 14 Ermittelt wurden zu jedem Lager in den normierten Laufversuchen die Laufzeiten bis zum Ausfall, also die Zeit, bis das Lager betriebsbedingt nicht mehr einsatzfähig war, sei es, dass ein makroskopisch Schaden erfasst wurde, sei es, dass WECs erfasst wurden. 6 45 1 14 The lifetimes to failure, ie the time until the warehouse was no longer operational due to operational reasons, were determined for each bearing in the standardized running tests, be it that a macroscopic damage was recorded, be it that WECs were recorded.
Ersichtlich konnte durch Verwendung des erfindungsgemäßen Ni-haltigen untereutek- toiden Vergütungsstahls in Verbindung mit der erfindungsgemäßen Herstellroute respektive insbesondere dem induktiven Randschichthärten eine beachtliche Verbesserung der Laufzeit erreicht werden, verglichen mit den martensitischen Axiallagerschei- ben aus 100Cr6. Es ergibt sich eine Laufzeitsteigerung von mehr als einem Faktor 2, wie sich aus einem Vergleich der gemittelten Laufzeiten ergibt. Bei den Lagern aus 100Cr6 ergibt sich eine über alle 6 Lager ermittelte durchschnittliche Laufzeit von 43h, während sich bei den erfindungsgemäßen Lagern eine durchschnittliche Laufzeit von 98 h ergibt, als von mehr als dem Doppelten. By using the Ni-containing hypoeutrogenic tempering steel according to the invention in conjunction with the production route according to the invention or, in particular, the inductive surface hardening, a considerable improvement in the transit time could be achieved, compared with the martensitic thrust bearing disks made of 100Cr6. The result is a runtime increase of more than a factor of 2, as results from a comparison of the average maturities. The bearings made of 100Cr6 give an average transit time of 43h, calculated over all 6 bearings, while the bearings according to the invention have an average runtime of 98 hours, rather than more than twice that.
Die angestellten Vergleichsuntersuchungen zeigen, dass das erfindungsgemäße Verfahren respektive das erfindungsgemäße Wälzlagerbauteil eine deutliche Verbesserung der Robustheit gegen die Bildung von WECs zeigt. Dies zeigt auch die in der Zeichnung dargestellte Weibull-Darstellung der Messwerte. Aufgetragen ist längs der Abszisse die Lebensdauer, also die Betriebsdauer bis zum Ausfall und längs der Ordinate der sogenannte Unreliability-Wert, der die Ausfallwahrscheinlichkeit Hi in Prozent angibt, jeweils logarithmisch. Die Weibull-Verteilung stellt eine allgemeine Verteilung dar. The employed comparative investigations show that the method according to the invention respectively the rolling bearing component according to the invention shows a clear improvement of the robustness against the formation of WECs. This is also shown by the Weibull representation of the measured values shown in the drawing. Plotted along the abscissa is the life, ie the operating time to failure and along the ordinate the so-called unreliability value, which indicates the probability of failure Hi in percent, each logarithmic. The Weibull distribution represents a general distribution.
Die Summenhäufigkeit Hi ermittelt sich wie folgt: Hi = (i - 0,3) : (n + 0,4) mit: The cumulative frequency Hi is calculated as follows: Hi = (i - 0.3): (n + 0.4) with:
i = Ordnungszahl des Ausfalls (hier: 1 ... 6) i = ordinal number of failure (here: 1 ... 6)
n = Anzahl an Proben (hier: 6) Die als Vierecke dargestellten Messwerte (■) geben die Werte für die aus 100Cr6 gefertigten Wälzlager respektive Axialscheiben an. Die rautenförmigen Symbole (♦) geben die Messwerte für die erfindungsgemäßen Wälzlagerbauteile respektive Axialscheiben wieder. Dargestellt ist jeweils auch eine Fitgerade. n = number of samples (here: 6) The measured values (■) shown as squares indicate the values for the rolling bearings or axial discs made of 100Cr6. The diamond-shaped symbols (♦) represent the measured values for the rolling bearing components according to the invention or axial disks. Also shown is a fitness straight.

Claims

geänderte Patentansprüche (Stand 07.09.2017) amended claims (as of 07.09.2017)
1 . Verfahren zur Herstellung eines Wälzlagerrings mit verbesserter Robustheit gegen die Bildung von White Etching Cracks (WEC), wobei der Wälzlagerring aus einem untereutektoiden Vergütungsstahl enthaltend C zu 0,4 - 0,55 % und1 . A method for producing a rolling bearing ring with improved resistance to the formation of white etching cracks (WEC), wherein the rolling bearing ring of a hypoeutectoid tempering steel containing C at 0.4 - 0.55% and
Cr zu 0,5 - 2,0 % zur Ausbildung einer gehärteten Randschicht induktiv erwärmt, anschließend abgeschreckt und anschließend angelassen wird, dadurch gekennzeichnet, dass das Erwärmen bei einer Frequenz von 8 - 1 1 kHz, insbesondere von 9 - 10 kHz, für eine Dauer von 3 - 10 s, insbesondere 4 - 7 s, erfolgt. Cr is inductively heated to 0.5-2.0% to form a hardened surface layer, then quenched and then tempered, characterized in that heating at a frequency of 8-1 1 kHz, in particular 9-10 kHz, for a Duration of 3 - 10 s, especially 4 - 7 s, takes place.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass der verwendete Vergütungsstahl einen Gehalt an Ni von 0,5 - 1 ,0 % aufweist. 2. The method according to claim 1, characterized in that the tempering steel used has a content of Ni of 0.5 to 1, 0%.
3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, dass ein Vergütungsstahl auf Basis von 50CrMo4 mit einem Ni-Gehalt zwischen 0,5 - 1 ,0 % verwendet wird. 3. The method according to claim 2, characterized in that a tempering steel based on 50CrMo4 with a Ni content between 0.5 - 1, 0% is used.
4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, dass ein Vergütungs- stahl mit folgender Zusammensetzung verwendet wird (Angaben in %): 4. The method according to claim 3, characterized in that a tempering steel is used with the following composition (in%):
C: 0,45  C: 0.45
Si: 0,23  Si: 0.23
Mn: 0,64  Mn: 0.64
P: 0,004  P: 0.004
S: 0,001  S: 0.001
Cr: 1 , 18  Cr: 1, 18
Mo: 0,28  Mo: 0.28
Ni: 0,75  Ni: 0.75
Cu: 0, 12  Cu: 0, 12
AI: 0,02  AI: 0.02
sowie ein Rest aus Eisen und Spurenelementen.  and a balance of iron and trace elements.
5. Verfahren nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass das induktive Erwärmen derart erfolgt, dass sich eine gehärtete Randschicht von wenigstens 0,2 mm Dicke bis höchstens 8 mm Dicke ausbildet. 5. The method according to any one of the preceding claims, characterized in that the inductive heating is carried out such that a hardened Forming edge layer of at least 0.2 mm thickness to at most 8 mm thickness.
Verfahren nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass das Erwärmen derart erfolgt, dass im gehärteten Randbereich eine Druckeigenspannung von wenigstens 300 MPa gegeben ist. Method according to one of the preceding claims, characterized in that the heating takes place in such a way that in the hardened edge region a compressive residual stress of at least 300 MPa is given.
Verfahren nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass das Anlassen bei einer Temperatur von 120 - 180 °C, insbesondere bei 130 - 150°C für eine Dauer von 1 - 4 h, insbesondere 2 - 3 h erfolgt. Method according to one of the preceding claims, characterized in that the tempering takes place at a temperature of 120-180 ° C, in particular at 130-150 ° C for a period of 1-4 hours, in particular 2-3 hours.
Wälzlagerring, hergestellt nach dem Verfahren nach einem der vorangehenden Ansprüche, bestehend aus einem untereutektoiden Vergütungsstahl enthaltend C zu 0,4 - 0,55 % und Cr zu 0,5 - 2,0 % mit einer durch induktives Härten ausgebildeten gehärteten Randschicht. Rolling ring produced by the method according to one of the preceding claims, consisting of a hypoeutectoid tempering steel containing C at 0.4 - 0.55% and Cr at 0.5 - 2.0% with a hardened surface layer formed by inductive hardening.
Wälzlagerring nach Anspruch 9, dadurch gekennzeichnet, dass der Vergütungsstahl ein Stahl auf Basis von 50CrMo4 mit einem Ni-Gehalt zwischen 0,5 - 1 ,0 % ist, und vorzugsweise folgende Zusammensetzung besitzt (Angaben inRolling bearing ring according to claim 9, characterized in that the tempering steel is a steel based on 50CrMo4 with a Ni content between 0.5 - 1, 0%, and preferably has the following composition (in
%): %):
C: 0,45  C: 0.45
Si: 0,23 Si: 0.23
Mn: 0,64 Mn: 0.64
P: 0,004 P: 0.004
S: 0,001 S: 0.001
Cr: 1 , 18 Cr: 1, 18
Mo: 0,28 Mo: 0.28
Ni: 0,75 Ni: 0.75
Cu: 0, 12 Cu: 0, 12
AI: 0,02 AI: 0.02
sowie ein Rest aus Eisen und Spurenelementen. and a balance of iron and trace elements.
EP17811833.7A 2016-11-09 2017-11-07 Method for producing a rolling bearing ring having an improved robustness against the formation of white etching cracks (wec) Active EP3538678B1 (en)

Applications Claiming Priority (2)

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DE102016221993.6A DE102016221993B4 (en) 2016-11-09 2016-11-09 Method for producing a rolling bearing ring with improved robustness against the formation of white etching cracks (WEC)
PCT/DE2017/100943 WO2018086658A1 (en) 2016-11-09 2017-11-07 Method for producing a rolling bearing ring having an improved robustness against the formation of white etching cracks (wec)

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DE102022117646A1 (en) 2022-07-14 2024-01-25 Schaeffler Technologies AG & Co. KG Thin ring bearing and computer tomograph with such a thin ring bearing
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DE4420092C3 (en) 1994-06-09 2001-08-09 Daimler Chrysler Ag Process for manufacturing a built camshaft with induction hardened cams
JPH09329147A (en) 1996-04-10 1997-12-22 Nippon Seiko Kk Water resistant long-life rolling bearing
JP2001220643A (en) * 2000-02-04 2001-08-14 Nisshin Steel Co Ltd Medium or high carbon steel sheet excellent in local ductility
DE102005060113B4 (en) 2004-12-23 2016-08-04 Schaeffler Technologies AG & Co. KG Wheel bearing and method for producing the same
GB0719456D0 (en) 2007-10-04 2007-11-14 Skf Ab Rolling element or ring formed from a bearing steel
JP5163183B2 (en) * 2008-02-27 2013-03-13 日本精工株式会社 Rolling bearing
BE1018151A5 (en) 2008-05-20 2010-06-01 Hansen Transmissions Int METHOD FOR INCREASING THE TIRES OF STRENGTH OF A MAINLY STEEL TOOL PART AND / OR REDUCING THE INCLUSION TO CREATE CALLED "WHITE ETCHING CRACKS" OR BRITTLE FLAKES IN SUCH SAMPLES.
EP2573195B1 (en) 2011-09-23 2014-10-22 ZF Wind Power Antwerpen NV Method for increasing the fatigue resistance of a steel roller bearing
WO2015199599A1 (en) 2014-06-27 2015-12-30 Aktiebolaget Skf Method for surface hardening a metal component
CN104232875B (en) 2014-07-17 2016-06-15 北京科技大学 A kind of Technology for Heating Processing of shield machine 3m bearing ring

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US20200300303A1 (en) 2020-09-24
DE102016221993A1 (en) 2018-05-09
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ES2906851T3 (en) 2022-04-20
DK3538678T3 (en) 2022-03-07

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